The overall objective of this contract is to identify, and clone tumor suppressor genes in B6C3Fl mice. This includes the identification of polymorphic probes in the B6C3F1 mouse using Probes that have been mapped to chromosomes in the mouse or other species; identify mouse chromosomes that show a loss of heterozygosity in specific tumor tissue DNAs using RFLP probes; reprobe membranes with selected oncogene probes to determine if certain oncogenes are amplified in tumors studied.